Graphical system and method for automatically scaling waveforms in a signal measurement system

ABSTRACT

A signal scaling system and methodology for use in a signal measurement system such as a digital or analog oscilloscope, logic analyzer, network analyzer, spectrum analyzer or waveform generator that has a graphical user interface which controls a waveform display region on a display device. The signal scaling system determines one or more displayed waveform scaling parameters to cause portions of selected displayed waveforms appearing within a rescaling rectangle to occupy a predetermined portion of the waveform display region other than the rescaling rectangle. For each of the selected displayed waveforms, the scaling parameters may include horizontal scaling, horizontal offset, vertical scaling and vertical offset. Preferably, the predetermined portion of the waveform display region comprises the entire waveform display region and the selected displayed waveforms include all waveforms at least partially within the rescaling rectangle. The displayed waveforms may include signal waveforms, function waveforms, and memory waveforms and the signal measurement system is preferably a digital oscilloscope. The signal scaling system includes an resealing rectangle specification unit for outlining an resealing rectangle on the waveform display region between user-specified start and end points. A scaling computation unit calculates the displayed waveform scaling parameters based upon specifications of the rescaling rectangle generated by the rescaling rectangle specification unit and current scaling parameters generated by the signal measurement system.

This application is a continuation of application Ser. No. 08/863,995,filed May 27, 1997, entitled GRAPHICAL SYSTEM AND METHOD FORAUTOMATICALLY SCALING WAVEFORMS IN A SIGNAL MEASUREMENT SYSTEM, nowpending.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to signal measurement systemsand, more particularly, to scaling displayed waveforms in signalmeasurement systems.

2. Related Art

Conventional signal measurement systems such as digital oscilloscopessample, record and display time-varying analog signals. Samples of aninput signal are taken and quantized, and the resultant digitalrepresentations are stored in a waveform memory under the control of asampling clock. The acquired data may subsequently be read out aslocations in memory are sequentially addressed by a clock signal toprovide digital data which can be converted to a time-varying outputsignal for a waveform display. The sampling clock may be operated at oneof several selectable rates depending upon the frequency content of theinput signal. The selection of the portion of the analog input signalwhich is sampled and stored is determined by appropriate triggeringcircuitry to enable the operator to display the desired portion of thewaveform.

There are many types of display elements which can be presented insignal measurement systems in general and test and measurementinstruments in particular. For example, in addition to the waveformsrepresenting the signals currently received at the channel inputs,waveforms referred to as function waveforms may also be displayed.Function waveforms are waveforms created by processing the signalwaveforms such as performing arithmetic manipulations or combiningmultiple input signal waveforms in some predetermined manner. Theresulting waveforms are placed in a display memory for subsequentretrieval and display. In addition, memory waveforms may also bedisplayed. Memory waveforms are waveforms which have been stored inmemory for some predetermined time for later display. In addition to theabove waveforms, other display elements such as markers indicators,trigger indicators, etc. are typically displayed.

Conventional test and measurement systems typically provide a displaygrid on which the display elements are presented. The display griddivides the coordinate axes into a series of divisions. Waveforms aredisplayed on the display grid and are scaled vertically and horizontallyto facilitate analysis. Typically, the horizontal scale represents sweepspeed and is in units of seconds per division. The vertical scalerepresents signal amplitude and is in volts per division. The center ofthe horizontal axis represents the delay or horizontal position of thedisplayed waveform and is referred herein to as horizontal offset. Thecenter of the vertical axis represents the voltage offset of thedisplayed waveform and is referred to as vertical offset. The adjustmentof these parameters is generally referred to signal scaling or waveformscaling and the above parameters are referred to as scaling parameters.Thus there are four scaling parameters which are controlled by the userto capture a desired portion of a waveform and to achieve a desiredrelative display of multiple waveforms: horizontal scale, horizontaloffset, vertical scale and vertical offset.

Conventional test and measurement systems typically have one or moredials or knobs to control waveform scaling. Some conventional systemsprovide four knobs, one for each scaling parameter, for each inputchannel in the instrument. In test and measurement systems which have asingle time base generator, there are often vertical scale and offsetknobs dedicated to each channel and a single common knob dedicated tohorizontal scale and offset. In other types of conventional test andmeasurement systems there is just one set of knobs for vertical scaleand offset control. In this type of system, the user must first selectwhich waveform is to be modified in accordance with the knobadjustments. Other conventional signal scaling systems have a singlegeneral purpose knob that requires the user to assign to the knob both,the scaling parameter to be changed and the waveform to be modified. Theassignment of scaling parameters and/or waveforms to a knob may beachieved through activation of hardware and software switches.

There are a number of drawbacks to these conventional systems. First,there are numerous control actions required to assign parameters andwaveforms to individual knobs and numerous adjustments that have to bemade to achieve a desired scaling. This yields a complicated userinterface that is difficult to learn and operate. In addition, thesescaling parameters are adjusted independently; the user can typicallymodify only a single scaling parameter of a single waveform at a giventime. As a result, complete scaling operations require a minimum ofseveral control operations. In addition, it is not uncommon to return toa particular scaling parameter/waveform to make further modificationsafter other scaling parameters have been modified. Thus, becausemultiple controls are involved, these manipulations can be iterative innature, further complicating the use of the instrument. In addition,such iterative control operations often take considerable time, reducingthe utilization of the instrument for signal analysis and measurement.

Furthermore, the relationship between the numeric values associated withthe scaling control operation and the resulting effect on the displayedwaveform is unclear. Users often cannot anticipate the extent to which awaveform changes in size and/or position in response to a specificchange in a numeric value.

What is needed, therefore, is a simple, uncomplicated means for enablinga user to perform scaling operations on displayed waveforms quickly andeasily without having to perform a large number of control steps andoperations and which enables the user to anticipate the resulting effecton the displayed waveforms.

SUMMARY OF THE INVENTION

The present invention is a signal scaling system and methodology for usein a signal measurement system having a graphical user interface whichcontrols a waveform display region on a display device. In one aspect ofthe invention the signal scaling system is configured to determine oneor more displayed waveform scaling parameters to cause portions ofselected displayed waveforms appearing within the rescaling rectangle tooccupy a predetermined portion of the waveform display region other thanthe resealing rectangle. For each of the selected displayed waveforms,the scaling parameters include horizontal scaling, horizontal offset,vertical scaling and vertical offset. Preferably, the predeterminedportion of the waveform display region comprises the entire waveformdisplay region and the selected displayed waveforms include allwaveforms at least partially within the resealing rectangle. Thedisplayed waveforms may include signal waveforms, function waveforms,and memory waveforms and the signal measurement system is preferably adigital oscilloscope.

In one embodiment the signal scaling system includes an rescalingrectangle specification unit configured to outline a rescaling rectangleon the waveform display region between a user-specified start point anda user-specified end point. The start and end points are at opposingcorners of the rescaling rectangle. The signal scaling system alsoincludes a scaling computation unit configured to calculate thedisplayed waveform scaling parameters. This determination is based uponspecifications of the rescaling rectangle generated by the resealingrectangle specification unit and current scaling parameters generated bythe signal measurement system. In one embodiment, the start point is apixel location of a current cursor position upon receipt of a firstselection indication from the signal measurement system. Likewise, theend point is a pixel location of a current cursor position upon receiptof a second selection indication from the signal measurement system.Typically, the user selects a pixel location through the use of one ormore well-known pointing devices. Preferably, the scaling computationmodule determines the scaling parameters in response to a user action.

In another embodiment of the invention the rescaling rectanglespecification module includes a validation means for determining whethera valid pixel location has been selected as the start and end points.The validation determination is based upon cursor information providedby the signal measurement system. Valid pixel locations are consideredto be pixel locations between which the resealing rectangle may bedrawn. Preferably, a valid pixel location of the start point is locatedin a background region of the waveform display region.

In another embodiment of the invention, the validation means includes aninterfacing means for interfacing with the signal measurement system toobtain the cursor information. The cursor information includes a currentcursor position on the waveform display region and a selectionindication of when the user has selected a pixel location on thewaveform display region. The validation means also includes a hit-testmeans for determining whether the selected start point is sufficientlyfar from a display element to be considered to be within the backgroundregion of the waveform display region.

It is noted that the displayed waveform scaling parameters define arescaled representation of the portions of the selected displayedwaveforms while the rescaling rectangle is drawn over an originalrepresentation of the displayed waveforms. In one embodiment the scalingcomputation unit includes means for alternating between the originalrepresentation of the displayed elements and the rescaled representationof the portions of the selected displayed waveforms.

In another aspect of the invention, a signal measurement system isdisclosed. The signal measurement system includes a display; a graphicaluser interface for controlling the display to provide a waveform displayregion; and a signal scaling system configured to determine one or moredisplayed waveform scaling parameters to cause portions of selecteddisplayed waveforms appearing within the rescaling rectangle to occupy apredetermined portion of the waveform display region. In one embodimentthe rescaling rectangle is of a predetermined size optionally appearingin a predetermined location of the waveform display region. Thedisplayed waveforms may include signal waveforms, function waveforms,and memory waveforms.

In another embodiment, the signal measurement system includes anrescaling rectangle specification unit configured to outline a rescalingrectangle on the waveform display region between user-specified startand end points, which are at opposing corners of the resealingrectangle. In another embodiment, the signal measurement system alsoincludes a scaling computation unit. The scaling computation unit isconfigured to calculate the displayed waveform scaling parameters basedupon specifications of the resealing rectangle generated by theresealing rectangle specification unit and current scaling parametersgenerated by the signal measurement system. The start point ispreferably a pixel location of a current cursor position upon receipt ofa first selection indication from the signal measurement system whilethe end point is a pixel location of a current cursor position uponreceipt of a second selection indication from the signal measurementsystem.

The signal measurement system also includes an interfacing means forinterfacing with the signal measurement system to obtain the cursorinformation, the cursor information including a current cursor positionon the waveform display region and the selection indication of when theuser has selected a pixel location on the waveform display region. Ahit-test means determines whether the selected start point issufficiently far from a display element to be considered to be withinthe background region of the waveform display region.

Preferably, the predetermined portion of the waveform display regioncomprises the entire waveform display region. Alternatively, thepredetermined portion of the waveform display region comprises a largeror smaller region of the waveform display region, the larger regionbeing user-specified. The displayed waveform scaling parameters define aresealed representation of the portions of the selected displayedwaveforms. On the other hand, the resealing rectangle is drawn over anoriginal representation of the displayed waveforms. In one embodiment,the scaling computation unit includes means for alternating between theoriginal representation of the displayed elements and the resealedrepresentation of the portions of the selected displayed waveforms.

In another aspect of the invention, a digital oscilloscope is disclosed.The digital oscilloscope includes a display and a graphical userinterface for controlling said display to provide a waveform displayregion. The oscilloscope also includes a signal scaling systemconfigured to determine horizontal and vertical scaling and offsetscaling parameters to cause portions of displayed waveforms appearingwithin a user-created rescaling rectangle to occupy the entire waveformdisplay region. The signal scaling system includes an rescalingrectangle specification unit configured to outline the resealingrectangle on the waveform display region between a user-specified startpoint in a background region of the waveform display region and auser-specified end point. The signal scaling system also includes ascaling computation unit configured to calculate the scaling parametersbased upon specifications of the rescaling rectangle generated by theresealing rectangle specification unit and current scaling parametersgenerated by the digital oscilloscope. The signal scaling system furtherincludes means for alternating between an original representation of thedisplayed elements and a resealed representation of the displayedwaveforms.

In another aspect of the invention, a method for scaling waveforms in asignal measuring system having a display device and a graphical userinterface that controls a waveform display region on the display deviceis disclosed. The method includes the steps of: (a) generating anrescaling rectangle between a user-specified start pixel location and auser-specified end pixel location such that the start and end points areopposing corners of the rescaling rectangle; (b) calculating new scalingparameters in accordance with the resealing rectangle for displayedwaveforms within the rescaling rectangle; and (c) drawing a new waveformdisplay region such that the resealing rectangle occupies apredetermined larger portion of the waveform display region.

In one embodiment, the step (a) comprises the steps of: (1) detecting auser selection of a pixel location in a background region of thewaveform display region; (2) tracking the cursor until selection of theend point is detected; and (3) drawing the resealing rectangle betweenthe start and end points. In another embodiment, the step (b) comprisesthe step of: (1) calculating new scaling parameters in accordance withthe rescaling rectangle for displayed waveforms within the rescalingrectangle based upon horizontal and vertical coordinate values forcoordinates of the rescaling rectangle and a current vertical andhorizontal scaling of the displayed waveforms.

In still another embodiment, the method further includes the steps of:(d) providing a first toggle means of returning to an original scaling;(e) returning to the original representation of said display elementswhen the first toggle means is selected by the user; (f) providing asecond toggle means of returning to the rescaled representation of saiddisplay elements; and (g) returning to the rescaled representation ofthe display elements when said second toggle means is activated by theuser.

Further features and advantages of the present invention as well as thestructure and operation of various embodiments of the present inventionare described in detail below with reference to the accompanyingdrawings. In the drawings, like reference numbers indicate identical orfunctionally similar elements. Additionally, the left-most one or twodigits of a reference number identifies the drawing in which thereference number first appears.

BRIEF DESCRIPTION OF THE DRAWINGS

This invention is pointed out with particularity in the appended claims.The above and further advantages of this invention may be betterunderstood by referring to the following description taken inconjunction with the accompanying drawings, in which:

FIG. 1 is a functional block diagram of a digital oscilloscope suitablefor implementing the signal scaling system and method of the presentinvention;

FIG. 2 is a functional block diagram of one embodiment of the signalscaling system implemented in the digital oscilloscope illustrated inFIG. 1;

FIG. 3A is a diagram illustrating an exemplary waveform display regionshowing an rescaling rectangle created by the user in accordance withthe signal scaling system of the present invention and a singleexemplary waveform;

FIG. 3B is a diagram illustrating an exemplary waveform display regionrescaled in accordance with the rescaling rectangle illustrated in FIG.3A;

FIG. 4 is a flowchart of one embodiment of the signal scaling method ofthe present invention performed by the present invention whenimplemented in the digital oscilloscope illustrated in FIG. 1;

FIG. 5 is a flowchart of one embodiment of the processes performed tocreate an rescaling rectangle in accordance with the present invention;and

FIG. 6 is a flowchart of one embodiment of the processes performed torescale displayed waveforms in accordance with a user-created resealingrectangle.

DETAILED DESCRIPTION

The present invention is a signal scaling system and method that may beimplemented in any signal measurement system having a graphical userinterface controlling a waveform display. In one preferred embodiment ofthe present invention, the signal scaling system is implemented in atest and measurement instrument, such as a digital or analogoscilloscope, logic analyzer, network analyzer, spectrum analyzer orwaveform generator. FIG. 1 is a functional block diagram of an exemplarydigital oscilloscope suitable for implementing the signal scaling systemand method of the present invention.

The digital oscilloscope 100 is a commonly-available digitaloscilloscope designed to acquire, analyze and display a wide variety ofsignals generally in terms of the voltage of the signals versus time.The digital oscilloscope 100 preferably includes a general purposecomputer system, which is programmable using a high level computerprogramming language, and specially programmed, special purpose hardwarefor performing signal acquisition, analyze and display functions.

The digital oscilloscope 100 includes a processor 102, a memory unit104, input/output (I/O) interface cards 106, storage units (not shown)such as a hard disk drive and a floppy disk drive, one or more inputdevices such as front keyboard panel 108 and pointing devices 110 anddisplay 112. The memory 104 is used for storage of program instructionsand for storage of results of calculations performed by the processor102. In a preferred embodiment, the memory 104 includes random accessmemory (RAM). The display is preferably a liquid crystal display and islogically or physically divided into an array of picture elements(pixels). The input/output (I/O) interface cards 106 may be modem cards,network interface cards, sound cards, etc.

The processor 102 is typically a commercially available processor, suchas the PENTIUM microprocessor from INTEL Corporation, POWERPCmicroprocessor, SPARC processor, PA-RISC processor or 68000 seriesmicroprocessor. Many other processors are also available. Such aprocessor usually executes a program referred to as an operating system114, such as the various versions of the WINDOWS operating systems fromMICROSOFT Corporation, the NETWARE operating system available fromNOVELL, Inc., or the UNIX operating system available from many vendorssuch as SUN MICROSYSTEMS, Inc., HEWLETT-PACKARD and AT&T. The operatingsystem 114 controls the execution of other computer programs such as agraphical user interface (GUI) 116 and the signal scaling system 118,and provides scheduling, input-output control, file and data management,memory management, and communication control and related services. Theprocessor 102 and operating system 114 define a computer platform shownby dashes block 101, for which application programs in high levelprogramming languages are written. The functional elements of thedigital oscilloscope 100 communicate with each other via bus 120. Thedigital oscilloscope 100 includes a signal acquisition system 122, ascope interface 124 and video control 126. The signal acquisition system122 includes scaling and conditioning 128 that receives input signalsthrough channel inputs 130. The scaling and conditioning unit 128 andacquisition unit 132 include well-known high frequency electronics forsignal acquisition, signal conditioning, and analog-to-digitalconversion, all of which are controlled by the computer system 101 andare considered to be well-known in the art. The timebase 134 drives theanalog-to-digital conversion process performed in acquisition 132,specifying when to sample the input signals and how many samples are tobe taken. The trigger 136 synchronizes the acquisition process throughthe timebase 134, enabling the user to arrange a trigger event to obtaina stable waveform display of the desired features of one or more of theinput signals. Trigger 136 may be based upon a line sync or auxiliarytrigger input, as is well known in the art.

The waveform analyzer 138 performs measurement processes for developingthe waveform for display. It contains hardware and software to performwell-known operations such as setting the analog-to-digital codes forthe acquisition unit 132 and mapping the resulting digital informationto the physical pixel locations which are ultimately presented ondisplay 112 under the control of GUI 116. The pointing device 110 and/orthe keyboard 108 are used to move a cursor on the GUI-controlled display112 to select display elements under the cursor. The pointing devices110 may include any number of pointing devices such as a mouse,trackball or joy stick. Of course, the cursor may be controlled with oneor more keyboards 108 located externally or integrated into a frontpanel of the digital oscilloscope 100.

The scope interface card 124 includes a video controller 140 thatcontrols the rendering of pixels into the waveform random access memory(RAM) 142. It also receives display element control commands and cursorinput information from the front panel keyboard 108 and the pointingdevice(s) 110. The waveform RAM 142 includes a data structure for eachpixel location on the display 112. The data structures containinformation regarding every display clement that is to be drawn at eachpixel location. Although there may be multiple display elements whichare to be drawn at a given pixel location, only one color may berendered at that location. The waveform RAM 142 supplies the priorityencoder 144 with this information. The priority encoder 144 prioritizesthe competing display elements. For example, if the user arranged amarker and a waveform such that they are located in the same pixellocation, then the priority encoder 144 selects that display elementwith a highest predetermined priority. In such an example, the color ofthe marker is rendered at the pixel location providing a display thatappears to show the marker over the waveform. The priority encoder thensends the selected color to the VRAM 146 which then causes the pixel tobe rendered in the indicated color.

The video display controller 126 includes a dynamic random access memory(DRAM) 148 which contains data specifying a color for each pixel in thedisplay 112. Likewise, the video random access memory (VRAM) 146 alsocontains data specifying a color for each pixel in the display 112. Thecomputer system 101 controls the information in DRAM 148 while thesignal acquisition system 122 controls information in the VRAM 146. Foreach pixel in the display 112, the video controller 126 selects whetherthe pixel in the display 112 is specified from VRAM 146 or DRAM 148. Ingeneral, information in VRAM 146 includes digitized waveforms beinggenerated by the system 122 with high rates of change that are much toofast for software processing by the computer system 101 for real-timedisplay of the waveforms on display 112.

Video controller 126 includes a controller 150 and a multiplexer 152.Controller 150 controls which of the two inputs to the multiplexer 152are processed into display signals for transmission to the display 112under the control of the graphical user interface 116. The controller150 typically monitors color data sent from the DRAM 148 and may beprogrammed to switch the multiplexer 152 to a different input when aparticular programmed color is received from the DRAM 148. A rectangularpixel area is typically defined within DRAM 148 with the programmedcolor, typically dark gray. The programmed color is not displayed, butinstead serves as a data path switch control for the multiplexer 152.Therefore, within the programmed color rectangle, display data comesfrom VRAM 146. When various control functions are needed, an interactivedialog box is drawn within the programmed color rectangle.

The signal scaling system 118 implements a simple and intuitive methodfor rescaling waveform and other display elements presented on thedisplay 112 under the control of the GUI 116. The signal scaling system118 determines one or more displayed waveform scaling parameters tocause portions of selected displayed waveforms appearing within arescaling rectangle to occupy a predetermined portion of the waveformdisplay region other than the resealing rectangle. The software routinesfor performing the signal-scaling methodology in accordance with theinvention typically reside in memory 104 and/or disk storage devices,and may be stored on a computer-readable medium such as, for example,magnetic disk, compact disc or magnetic tape and may be loaded into thedigital oscilloscope 100 using an appropriate peripheral device as knownin the art.

Preferably, the signal scaling system 118 is implemented in anywell-known programming language such as C or C++. Those ski led in theart will appreciate that different implementations, including differentfunction names, programming languages, data structures, and/oralgorithms may also be used in embodiments of the present inventionother than those described below. It should be further understood thatthe invention is not limited to a particular computer platform,particular operating system, particular processor, or particular highlevel programming language, and that the hardware components identifiedabove are given by way of example only. The signal scaling system may beimplemented, for example, in dedicated hardware, firmware, or anycombination thereof.

A preferred implementation of the present invention is in test andmeasurement equipment having a graphical user interface 120, such as thedigital oscilloscope 100. A functional block diagram of one preferredembodiment of the signal scaling system 118 of the present inventionimplemented in the digital oscilloscope 100 is shown in FIG. 2. Thefunction and operation of the signal scaling system 118 will bedescribed with reference to an exemplary waveform scaling operationillustrated in FIGS. 3A and 3B.

As shown in FIG. 3A, a waveform display region 302 is divided into tendivisions along the horizontal axis 304 and eight divisions along thevertical axis 306. The horizontal axis 304 represents the sweep speedand is provided in units of microseconds per division. The horizontalscale is 1 microsecond per division and the horizontal extent is 10microseconds. The horizontal coordinate axis extends from 0 through 10microseconds and the horizontal offset is a 5 microseconds. The verticalaxis 306 represents signal amplitude and is in units of volts perdivision. The vertical scale is 1 volt per division and the verticalextent is 8 volts. The vertical coordinate axis extends from 0 through 8volts and the vertical offset is at 4 volts. A single pulse waveform 308is shown on the waveform display region 302. The signal pulse 308 risesfrom 3 to 6 volts at 3 microseconds and returns to 3 volts at 5microseconds. In FIG. 3A the waveform 308 is presented in the originalscaling while in FIG. 3B is the same waveform shown resealed, referredto as resealed waveform 312.

The signal scaling system 118 includes a rescaling rectanglespecification unit 202 that is responsive to a user-controlled cursorposition. The resealing rectangle specification unit 202 is configuredto outline a rectangularregion 310 of the waveform display region 302.In addition, the signal scaling system 118 includes a scalingcomputation module 204 configured to rescale all relevant displayelements in accordance with scaling parameters defined by therectangular region 310. This results in the portion of the displayelements contained within the rectangular region 310 occupying apredetermined portion of the waveform display region 302.

The resealing rectangle specification module 202 includes an interfacewith the digital oscilloscope 100 to obtain cursor information 201. Asnoted, the digital oscilloscope 100 is preferably a computer-basedsystem containing computer system 101. Typically, in such embodiments,display control and status information such as cursor information 201 isobtained from the operating system 114 running on the processor 102through the generation of well-known procedure calls.

The cursor information 201 includes a current position of the cursor onthe waveform display region 302 and an indication of when the user hasselected a pixel location on the waveform display region. The user mayselect a pixel location through well-known pointing devices introducedabove, such as a mouse, trackball, track-pad, joy stick, keyboard, etc.The module 202 determines whether a pixel location has been selected bythe user based upon these inputs in a well-known manner. Preferably, themodule 202 provides these inputs to a hit-test system as described incommonly owned U.S. Patent Application entitled “System and Method ForEfficient Hit-Testing in a Graphical User Interface,” naming as aninventor Jay A. Alexander and filed concurrently herewith under, thespecification of which is hereby incorporated by reference in itsentirety. The preferred hit-test system determines whether the user hasselected a cursor position that is sufficiently close to a displayelement to be considered a selection by the user of that display elementor a selection of a background region of the waveform display region. Itis understood, however, that the module 202 may include or interfacewith other means for determining whether a pixel location has beenselected by the user based upon the above and/or other inputs and usingother techniques now or later developed.

When the user has selected the background region on the waveform displayregion 302, the module 202 identifies the selected pixel location as astart point 312 from which the rescaling rectangle 310 will be drawn.The module 202 then calculates the rescaling rectangle 310 using thestarting point 312 and the current cursor position as opposingcoordinates of the rectangle 310. The rescaling rectangle specificationmodule 202 continually tracks the current cursor position as the cursoris dragged across the waveform display region by the user.

The rescaling rectangle specification module 202 periodically draws therescaling rectangle 310 on the waveform display region 302 as thecurrent cursor position is changed by the user until an end point 314 isreached. The module 202 periodically generates an rescaling rectanglerequest 203 that is provided to the operating system 114 to draw therescaling rectangle 310 on the waveform display region 302. Thegeneration of such a procedure call is considered to be well-known inthe art. This call preferably specifies a particular color and lineconfiguration, such as dashes, which clearly distinguishes the resealingrectangle 310 from the displayed waveforms and other display elements.

The rescaling rectangle request 203 is preferably a standardizedprocedure call containing two coordinates which specify the rescalingrectangle 310 to the operating system 114. In the exemplaryimplementation of the digital oscilloscope 100, these coordinates are(X_(left), Y_(bottom)) and (X_(right), Y_(top)) wherein X_(right) isalways greater than X_(left) and Y_(top) is always greater thanY_(bottom). In order to enable the user to select any pixel location asthe start point 312 and drag the cursor in any desired direction tocreate the rescaling rectangle 310, the system 118 “normalizes” theresealing rectangle 310 to the coordinate system 301 adopted by thegraphical user interface 116. This normalization converts the startingand ending points so that the above-noted relationship is satisfied.

Referring to FIG. 3A, there are four scenarios regarding the manner inwhich the user creates the rescaling rectangle 310. From a start point312, the user may drag the cursor through any one of the four quadrantssurrounding the start point 312. Since the start point 312 and the endpoint 314 have at least one coordinate value in common with normalizedpoints 316 and 318, the normalized points are easily determined. In theexample illustrated in FIG. 3A the user-selected start and end points312 and 314 are different than the normalized points 316 and 318,requiring a conversion to be performed. However, if the start and endpoints 312 and 314 are such that X_(right) is greater than X_(left) andY_(top) is greater than Y_(bottom), then they coincide with thenormalized points 316 and 318 and no conversion or normalization isnecessary.

During the creation of the rescaling rectangle 310, the displayedwaveforms and other display elements will continue to be presented inthe original scaling as shown in FIG. 3A. When the user completescreating the rescaling rectangle 310, the system 118 waits until theuser either activates or deselects the scaling operations of the presentinvention. The user preferably invokes waveform scaling through theselection of an arbitrary point within the resealing rectangle 312. Inalternative embodiments, a particular key stroke or menu item may beprovided as a means for the user to communicate this selection or theselection may occur automatically after the creation of the rescalingrectangle 310. Likewise, the user deselects waveform scaling preferablythrough the selection of an arbitrary point outside of the rescalingrectangle 310. In another preferred embodiment, the user may alsodeselect the scaling operations of the present invention by notperforming any actions for a predetermined period of time. In thisembodiment, such inactivity will cause the waveform scaling operationsof the present invention to time-out. When waveform scaling operationsare positively or passively deselected, the rescaling rectangle 310 isno longer presented on the waveform display region 302, returning theimplementing signal measurement system to a prior operational state.

As noted, the scaling computation module 204 rescales all relevantdisplay elements in accordance with scaling parameters defined by theuser-created rectangular region 310. That is, the selection of therescaling rectangle 310 identifies the region of the waveform displayregion 302 which the user desires to rescale so that the displayelements contained within the resealing rectangle 310 occupy the entirewaveform display region 302.

The scaling computation module 204 receives the rescaling rectanglecoordinates 211 from the module 202 and determines the new scalingparameters for the displayed waveforms in accordance with the rescalingrectangle 210 based upon the scaling information received from thesignal scaling and conditioning unit 128. The scaling computation module204 preferably determines the new scaling parameters in response to auser command or other action. This may be achieved through anywell-known means, such as selecting an arbitrary point within therescaling rectangle 310. Alternatively, the scaling computation module204 may determine the new scaling parameters without the user performingany function or additional step at all beyond the creation of therescaling rectangle 310.

The received scaling information is obtained by generating a volt/timequery 205 for the signal scaling and conditioning unit 128. The queryrequests the current vertical and horizontal scaling and the voltage andtime associated with the normalized rescaling rectangle coordinates 316and 318 for each displayed waveform. The signal scaling and conditioningunit 128 returns coordinate voltage/time information 207 to the scalingcomputation module 204. The calculations performed by the signal scalingsystem 118 of the present invention are described with reference to theexemplary resealing operation of the single exemplary waveform depictedin FIGS. 3A and 3B.

The new vertical scale 316 illustrated in FIG. 3B has a vertical scalingof 625 millivolts and ranges from 2.0 volts to 7.0 volts with a verticaloffset of 4.5 volts. Referring to FIG. 3A, this scaling represents theresealing rectangle 310 which extends from 2 volts through 7 volts alongthe vertical scale 306. Since the extent of the new vertical scale 320is 5 volts and it is divided into 8 divisions, then each division is 625millivolts. This is shown by:$V_{scale} = {\frac{\left( {7\quad {{div}.{- 2}}\quad {{div}.}} \right)\quad \left( {1\quad {{volt}/{{div}.}}} \right)}{8\quad {{div}.}} = {{625\quad {{milllivolts}/{{div}.V_{offset}}}} = {\frac{\left( {7\quad {{div}.{+ 2}}\quad {{div}.}} \right)\quad \left( {1\quad {{volt}/{{div}.}}} \right)}{2} = {4.5\quad {volts}}}}}$

The horizontal coordinate axis 314 illustrated in FIG. 3B has ahorizontal scaling of 400 nanoseconds per division and a horizontaloffset of 4 microseconds. Referring to FIG. 3A, this scaling representsthe rescaling rectangle 310 which extends from 2 microseconds through 6microseconds along the horizontal scale 304. Since the extent of the newhorizontal scale 322 is 4 microseconds and it is divided into 10divisions, then each division represents 400 nanoseconds. These valuesare calculated by the signal scaling system 118 as shown below.$H_{scale} = {\frac{\left( {{6\quad {div}} - {2\quad {div}}} \right)\quad \left( {1\quad {{\mu sec}/{{div}.}}} \right)}{10\quad {{div}.}} = {{400\quad {{nanoseconds}/{{div}.H_{offset}}}} = {\frac{\left( {{6\quad {div}} + {2\quad {div}}} \right)\quad \left( {1\quad {{\mu sec}/{div}}} \right)}{2} = {4\quad {microseconds}}}}}$

It should be understood that the rescaled plus signal 312 exhibits thesame amplitude and timing attributes as before the rescaling operationis performed. However, the contents of the rescaling rectangle 310completely occupies the waveform display region 302 shown in FIG. 3B.The contents of the rescaling rectangle 310 completely occupies thewaveform display region 302 as shown in FIG. 3B. That is, the portion ofthe original signal waveform 308 which extends beyond the boundaries ofthe rescaling rectangle 310 are not visible on the waveform displayregion 302 illustrated in FIG. 3B.

Note that in this illustrative example, only a single waveform isdisplayed and subsequently resealed in accordance with the presentinvention. It should be understood, however, that the above calculationsare to be performed on every waveform and other display elementscurrently displayed. For each such waveform different vertical and/orscaling and offset values are required to be calculated in order toachieve the desired rescaling as defined by the user through thecreation of the resealing rectangle 310. In systems which have a onetimebase generator 134, the signal waveforms all have the samehorizontal scaling. In such systems, the horizontal scaling is the sameand the new horizontal scaling is preferably determined for just onewaveform and utilized for all signal waveforms. On the other hand,because they are stored prior to viewing, the memory and functionwaveforms have independent horizontal scaling. In such systems, newhorizontal scaling must be determined for each displayed waveform. Thenew scaling information, including vertical and horizontal scaling foreach displayed waveform is output to the signal scaling and conditioningunit 128 as shown by new scaling command 209.

The scaling computation module 204 includes means for enabling the userto toggle between the original and new scaling. One preferred approachthat utilizes the graphical user interface 116 is to provide a dialogbox on the waveform display region providing the user with a graphicalmeans of returning to the original scaling. The dialog box, preferablylabeled “undo” will undo the scaling dictated by the rescaling rectangle310 and return the waveforms and display elements to their originalscaling. Selection of the dialog box causes the scaling computationmodule 204 to generate the appropriate calls to the signal scaling andconditioning unit 128 to display the originally-scaled waveforms.Preferably, the waveform display region also contains the rescalingrectangle 310 as originally drawn by the user to enable the user tovisually correlate the resealed waveforms and display elements to theregion enclosed by the rescaling rectangle 310 on the original display.

When the user returns to the original scaling, a dialog window entitled“redo” preferably accompanies the rescaled display to enable the user toreapply the rescaling parameters in accordance with the resealingrectangle 310. Thus, the user may toggle between the original and newscaling through the selection of the undo/redo dialog windows. It isunderstood that there are many other methods and techniques that may beutilized to provide user-activated functions such as the undo and redofunctions described above. These include, for example, selection of menuitems, key strokes, voice activation, and through the use of any type ofinput device now or later developed.

FIG. 4 is a flowchart of one embodiment of the automatic signal scalingprocess of the present invention. The automatic signal scaling process400 is started at block 402 when the user selects a pixel location thatis in the background region of the waveform display region. The user maymake such as election using the pointing device 110, front panelkeyboard 108 or any other well-known means. As noted, the selection ofthe background region is preferably determined by outputting the cursorinformation 201 received from the operating system 114 to the hit testsystem incorporated by reference above, although other approaches may beused. Once the user has selected a pixel location in the backgroundregion, then at block 404 the signal scaling system 118 generates anresealing rectangle 310 using the selected pixel location as a startpoint 312 and the current cursor position as an opposing comer of therescaling rectangle 310. The processes performed at block 404 aredescribed in detail below with reference to FIGS. 5A and 5B. Once theuser completes the dragging of the cursor across the waveform displayregion and indicates that the selected region is to be magnified tooccupy the complete waveform display region, processing at block 406 isperformed.

At block 406, new scaling parameters are calculated in accordance withthe selected rescaling rectangle 310. The new scaling parameters aredetermined for all displayed waveforms based upon the horizontal andvertical coordinate values for normalized coordinates of the rescalingrectangle and the current vertical and horizontal scaling of thedisplayed waveforms.

Once the new scaling parameters for each of the displayed waveforms aredetermined, then the new waveform display region is drawn at block 408.The system 118 generates the new voltage and timing information which isreceived by the signal scaling and conditioning unit 128 to rescale eachof the displayed waveforms in accordance with the expanded rectangle310. The expanded rectangle 310, including the display elementspositioned within the rectangle 310, are magnified to completely occupythe waveform display region 302. The automatic signal scaling process ofthe present invention then ceases at stop block 410.

The process performed by the present invention to create the rescalingrectangle 310 described above with reference to block 404 are describedin detail hereinbelow with reference to the flowchart shown in FIGS. 5Aand 5B. The process 404 is described with reference to the exemplaryresealing rectangle 310 introduced above.

The process 404 begins at start block 502 when the signal scalingoperations of the present invention are invoked or activated by theuser. As noted, this is preferably through the selection of a pixellocation in the background region of the waveform display region 302,although other techniques may be used. After start block 502, theprocess 404 advances to block 504 whereat the start point 312 of therescaling rectangle 310 is determined. The start point 312 is determinedto be the current cursor position when the cursor information 201received from the operating system 114 indicates that the user hasselected a pixel location in the background region of the waveformdisplay region. Once the start point 312 is determined, the automaticsignal scaling system 118 continually tracks the current cursor positionat block 506. The system 118 continues to receive the current positionfor the cursor as it is moved or dragged across the waveform displayregion by the user.

At block 508, the rescaling rectangle 310 is calculated based upon thecurrent cursor position received at block 506 and the start point 312determined at block 504. The resealing rectangle 310 is drawn with thecurrent cursor position and the start point as opposing corners of arectangle. As noted, the endpoints of the rescaling rectangle may needto be converted to a format appropriate for the graphical user interface116. A normalization process is performed at block 510 as describedabove, resulting in the two normalized points 316 and 318 which specifythe rescaling rectangle 310.

The rescaling rectangle 310 is drawn at block 512. Here, the signalscaling signal 118 generates an appropriate call to the operating system114 to draw the rescaling rectangle 310. Preferably the rescalingrectangle 310 is clearly distinguished from the displayed waveforms andother display elements.

The above process is continued as the cursor is dragged across thewaveform display region until an indication that the user has createdthe desired rescaling rectangle is received at block 514. In theembodiment wherein the pointing device 110 is a mouse, this may be whenthe user has released the mouse button during the dragging of thecursor. Other selection indications appropriate for the implementedpointing device 110 may b used. This data is received as part of thecursor information 201 as noted above.

After the user has selected a rescaling rectangle 310, the rectangle isdisplayed on the display 112 and the displayed waveforms and otherdisplay elements will continue to be presented in the original scaling.This condition will continue until the user either activates thewaveform scaling operations of the present invention or deslects thewaveform scaling feature. At block 516, the automatic signal scalingsystem 118 monitors the user's actions to determine if the signalscaling operations are to be invoked. In a preferred embodiment, theuser may invoke signal scaling through the selection of an arbitrarypoint within the resealing rectangle 312 although alternative methodsmay be used.

If the waveform scaling operations of the present invention are notinvoked at block 516, then at block 520 a determination is made as towhether the user has deselected waveform scaling operations. In apreferred embodiment, the user may deselect waveform scaling simply byselecting a point on the waveform display region that is not containedwithin the rescaling rectangle 310 or, preferably, by performing nooperation for a predetermined period of time. Other deselection methodsand techniques may be used as is known in the art. If it is determinedat block 520 that the user deselects the waveform scaling function ofthe present invention, then the rescaling rectangle 312 is removed fromthe waveform display region at block 522 and processing completes atblock 524.

If it is determined that the user has proceeded to invoke the waveformscaling operations at block 516, then processing continues at block 518whereat the normalized coordinates 316 and 318 for the resealingrectangle 310 are provided to the scaling computation module 204.Processing then completes at block 524.

As noted, the process performed by the present invention to determinethe new scaling parameters for the displayed waveforms is performed atblock 406. This process is described in detail herein below withreference with the flowchart shown in FIGS. 6A and 6B. As with theflowcharts illustrated in FIGS. 4 and 5, the process 406 is describedwith reference to the exemplary rescaling rectangle 310 introducedabove.

The new scaling operations are invoked at start block 602 when the userhas created the rescaling rectangle 310 and has activated the signalscaling operations of the present invention. As noted, this may beachieved through any well-known means, such as selecting an arbitrarypoint within the rescaling rectangle 310 or by performing no function oradditional step at all beyond the creation of the resealing rectangle310. At block 604, the automatic signal scaling system 118 selects adisplayed waveform. The signal scaling and conditioning unit 128 isqueried for the current scaling information at block 606 and thehorizontal and vertical coordinate values associated with the twonormalized point 316 and 318 for the selected waveform. The requestedinformation is received and the new vertical scale is calculated atblock 608 as described above.

As noted, the horizontal scaling of the waveforms may be linkedhorizontally due to the common time base in the implementing test andmeasurement system. Horizontal independence is determined at block 610.If such is the case and the new horizontal scaling has been previouslydetermined, then processing continues at block 614, skipping the block612 wherein the new horizontal scaling is determined as described above.At block 614, the new scaling information, including vertical andhorizontal scaling for the waveform selected at block 604 is output tothe signal scaling and conditioning unit 128.

If there are any displayed waveforms remaining to be scaled, asdetermined at block 616, then the above processes are repeated for eachof the remaining waveforms until all waveforms have been rescaled. Onceall the waveforms have been resealed, then processing continues at block618 to determine whether waveform scaling of the present invention hasbeen deselected. If so, then processing ceases at block 620.

Otherwise, processing continues at block 622 whereat an “undo” dialogwindow is drawn on the waveform display region 302 providing the userwith a graphical means of returning to the original scaling. The system118 monitors, at block 624, whether the user selects the dialog boxthrough the appropriate calls to the operating system 114. If it isdetermined that the user has selected the undo dialog box, thenprocessing continues at block 626.

At block 626 the scaling dictated by the rescaling rectangle 310 isreplaced by the original scaling and the waveforms and display elementsarc returned to their original scaling. This display preferably alsocontains the resealing rectangle 310 as originally drawn by the user forreasons noted above.

When the user returns to the original scaling, a dialog window entitled“redo” preferably accompanies the rescaled display to enable the user toreapply the rescaling parameters in accordance with the rescalingrectangle 310. This dialog box is drawn at block 628. At block 630 theuser's selection of the redo dialog box is monitored. If selected, thenprocessing continues at block 618. Otherwise, the new scaling remainsdisplayed. Thus, the user may toggle between the original and newscaling through the selection of the undo/redo dialog windows.

While various embodiments of the present invention have been describedabove, it should be understood that they have been presented by way ofexample only, and not limitation. For example, as noted, it ispreferable that the rescaling rectangle 310 is user-created through theuse of a cursor control device. Alternatively, the user may delineatethe boundaries of the rescaling rectangle using marker indicators orthrough the use of any other well-known graphical or other means. Asnoted, it is preferred that the user be given the means to dynamicallyselect the rescaling rectangle and determine its size and location,enabling the user to capture the display elements of interest.Alternative embodiments include previously-determined and storedrescaling rectangles for retrieval and application to a current waveformdisplay. These predetermined rescaling rectangles provide “fixed zooms”that may be about any predetermined portion of the waveform display. Inaddition, it was noted that in the preferred embodiment the resealingrectangle is expanded to occupy the entire waveform display region. Inalternative embodiments, this will not be the entire waveform display,enabling multiple rescaling rectangles to be displayed simultaneously,to allocate portions of the waveform display region to other uses, etc.Thus, the breadth and scope of the present invention should not belimited by any of the above-described exemplary embodiments, but shouldbe defined only in accordance with the following claims and theirequivalents.

What is claimed is:
 1. A signal scaling system for use in a signalmeasurement system having a graphical user interface controlling awaveform display region on a display device, said signal scaling systemconfigured to cause portions of selected displayed waveforms appearingwithin a resealing rectangle to occupy a predetermined portion of thewaveform display region other than said resealing rectangle, wherein auser-specified start point and a user-specified end point defineopposing corners of said resealing rectangle on the waveform displayregion.
 2. The signal scaling system of claim 1, comprising: a resealingrectangle specification unit, for generating waveform scalingparameters, configured to outline the resealing rectangle on thewaveform display region between the user-specified start and end points.3. The signal scaling system of claim 2, further comprising: a scalingcomputation unit configured to calculate one or more displayed waveformscaling parameters, to cause said portions of selected displayedwaveforms to occupy said predetermined portion of the waveform displayregion.
 4. The signal scaling system of claim 3, wherein said scalingcomputation unit uses scaling parameters generated by the signalmeasurement system to calculate said one or more displayed waveformscaling parameters.
 5. The signal scaling system of claim 3, wherein,for each of said selected displayed waveforms, said one or more scalingparameters comprises: horizontal scaling; horizontal position; verticalscaling; and vertical offset.
 6. The signal scaling system of claim 3,wherein one or more of said scaling parameters is specified by the user.7. The signal scaling system of claim 2, wherein said rescalingrectangle specification unit comprises: validation means for determiningwhether a valid pixel location has been selected as said start and endpoints based upon cursor information provided by the signal measurementsystem, said valid pixel locations being pixel locations between whichsaid resealing rectangle may be drawn.
 8. The signal scaling system ofclaim 7, wherein one or more of said valid pixel locations is located ina background region of said waveform display region.
 9. The signalscaling system of claim 3, wherein said one or more displayed waveformscaling parameters define a rescaled representation of said portions ofsaid selected displayed waveforms, and wherein said resealing rectangleis drawn over an original representation of said displayed waveforms,wherein said scaling computation unit comprises: means for alternatingbetween said original representation of said displayed elements and saidrescaled representation of said portions of said selected displayedwaveforms.
 10. The signal scaling system of claim 1, wherein the signalmeasurement system is a digital oscilloscope.
 11. A signal scalingsystem for use in a signal measurement system having a graphical userinterface controlling a waveform display region on a display device,said signal scaling system configured to determine one or more displayedwaveform scaling parameters to cause portions of selected displayedwaveforms appearing within an resealing rectangle to occupy apredetermined portion of the waveform display region other than saidresealing rectangle, wherein said one or more displayed waveform scalingparameters define a rescaled representation of said portions of saidselected displayed waveforms, and wherein said resealing rectangle isdrawn over at least a portion of the original representation of saiddisplayed waveforms.
 12. The signal scaling system of claim 11, furthercomprising: a resealing rectangle specification unit, for generatingwaveform scaling parameters, configured to outline the resealingrectangle on the waveform display region between the user-specifiedstart and end points.
 13. The signal scaling system of claim 12, furthercomprising: a scaling computation unit configured to calculate said oneor more displayed waveform scaling parameters, to cause said portions ofselected displayed waveforms to occupy said predetermined portion of thewaveform display region.
 14. The signal scaling system of claim 13,wherein said scaling computation unit uses current scaling parametersgenerated by the signal measurement system to calculate said waveformscaling parameters.
 15. The signal scaling system of claim 12, wherein,for each of said selected displayed waveforms, said one or more waveformscaling parameters comprises: horizontal scaling; horizontal position;vertical scaling; and vertical offset.
 16. The signal scaling system ofclaim 12, wherein one or more of said waveform scaling parameters isspecified by the user.
 17. The signal scaling system of claim 12,wherein said resealing rectangle specification unit comprises:validation means for determining whether a valid pixel location has beenselected as said start and end points based upon cursor informationprovided by the signal measurement system, said valid pixel locationsbeing pixel locations between which said resealing rectangle may bedrawn.
 18. The signal scaling system of claim 17, wherein one or more ofsaid valid pixel locations is located in a background region of saidwaveform display region.
 19. The signal scaling system of claim 13,wherein said one or more displayed waveform scaling parameters define arescaled representation of said portions of said selected displayedwaveforms, and wherein said rescaling rectangle is drawn over anoriginal representation of said displayed waveforms, wherein saidscaling computation unit comprises: means for alternating between saidoriginal representation of said displayed elements and said rescaledrepresentation of said portions of said selected displayed waveforms.20. The signal scaling system of claim 11, wherein the signalmeasurement system is a digital oscilloscope.
 21. A signal measurementsystem, comprising: a display; a graphical user interface foridentifying a portion of a selected waveform by specify opposing cornersof a resealing rectangle; and a signal scaling system configured todetermine one or more displayed waveform scaling parameters to cause apredetermined display region to be occupied by the portion of theselected waveform, wherein the predetermined display region is drawnover at least a portion of the selected waveform.
 22. The signalmeasurement system of claim 21, comprising: an resealing rectanglespecification unit configured to outline a resealing rectangle on thewaveform display region between a user-specified start point and auser-specified end point, said start and end points being at opposingcorners of said resealing rectangle.
 23. The signal measurement systemof claim 22, further comprising: a scaling computation unit configuredto calculate said one or more displayed waveform scaling parametersbased upon specifications of said resealing rectangle generated by saidrescaling rectangle specification unit and current scaling parametersgenerated by the signal measurement system.
 24. The signal measurementsystem of claim 21, wherein said predetermined portion of the waveformdisplay region comprises the entire waveform display region.
 25. Thesignal measurement system of claim 21, wherein said predeterminedportion of the waveform display region comprises a different size regionof said waveform display region, said different size region beinguser-specified.
 26. The signal measurement system of claim 23, furthercomprising: interfacing means for interfacing with the signalmeasurement system to obtain said cursor information, said cursorinformation including a current cursor position on the waveform displayregion and said selection indication of when the user has selected apixel location on the waveform display region; and hit-test means fordetermining whether said selected start point is sufficiently far from adisplay element to be considered to be within said background region ofsaid waveform display region.
 27. The signal measurement system of claim21, wherein said one or more displayed waveform scaling parametersdefine a rescaled representation of said portions of said selecteddisplayed waveforms, and wherein said resealing rectangle is drawn overan original representation of said displayed waveforms, wherein saidscaling computation unit comprises: means for alternating between saidoriginal representation of said displayed elements and said rescaledrepresentation of said portions of said selected displayed waveforms.28. The signal measurement system of claim 21, wherein said displayedwaveforms comprises signal waveforms, function waveforms, and memorywaveforms.
 29. A digital oscilloscope for use in a signal measurementsystem having a graphical user interface controlling a waveform displayregion on a display device, said signal scaling system configured tocause portions of selected displayed waveforms appearing within aresealing rectangle to occupy a predetermined portion of the waveformdisplay region other than said resealing rectangle, wherein auser-specified start point and a user-specified end point defineopposing corners of said resealing rectangle on the waveform displayregion.
 30. The digital oscilloscope of claim 29, comprising: aresealing rectangle specification unit, for generating waveform scalingparameters, configured to outline the resealing rectangle on thewaveform display region between the user-specified start and end points.31. The digital oscilloscope of claim 30, further comprising: a scalingcomputation unit configured to calculate one or more displayed waveformscaling parameters, to cause said portions of selected waveforms tooccupy said predetermined portion of the waveform display region. 32.The digital oscilloscope of claim 31, wherein scaling computation unituses scaling parameters generated by the signal measurement system tocalculate one or more displayed waveform scaling parameters.
 33. Adigital oscilloscope, comprising: a display; a graphical user interfacefor controlling said display to provide a waveform display region; and asignal scaling means configured to determine horizontal and verticalscaling and offset scaling parameters to cause portions of displayedwaveforms appearing within a user-created resealing rectangle to occupya predetermined portion of the waveform display region, including, anresealing rectangle specification means configured to outline saidresealing rectangle on the waveform display region between auser-specified start point in a background region of the waveformdisplay region and a user-specified end point; and a scaling computationmeans configured to calculate said scaling parameters based uponspecifications of said resealing rectangle generated by said resealingrectangle specification unit and current scaling parameters generated bythe digital oscilloscope.
 34. The signal scaling system of claim 33,wherein said a signal scaling system further comprises: means foralternating between an original representation of said displayedelements and a rescaled representation of said selected displayedwaveforms.
 35. A method for scaling waveforms in a signal measuringsystem having a display device and a graphical user interface thatcontrols a waveform display region on the display device, comprising thesteps of: (a) generating an resealing rectangle between a user-specifiedstart pixel location and a user-specified end pixel location such thatsaid start and end points are opposing corners of said resealingrectangle; (b) calculating new scaling parameters in accordance withsaid resealing rectangle for displayed waveforms within said resealingrectangle; and (c) drawing a new waveform display region such that saidresealing rectangle occupies a predetermined portion of the waveformdisplay region that is different in size than the waveform displayregion.
 36. The method of claim 35, wherein said step (a) comprises thesteps of: (1) detecting a user selection of a pixel location in abackground region of the waveform display region; (2) tracking thecursor until selection of said end point is detected; and (3) drawingsaid resealing rectangle between said start and end points.
 37. Themethod of claim 35, wherein said step (b) comprises the step of: (1)calculating new scaling parameters in accordance with said resealingrectangle for displayed waveforms within said resealing rectangle basedupon horizontal and vertical coordinate values for coordinates of saidresealing rectangle and a current vertical and horizontal scaling of thedisplayed waveforms.
 38. The method of claim 35, further comprising thesteps of: (d) providing a first toggle means of returning to an originalscaling; (e) returning to said original representation of said displayelements when said first toggle means is selected by the user; (f)providing a second toggle means of returning to said rescaledrepresentation of said display elements; and (g) returning to saidrescaled representation of said display elements when said second togglemeans is activated by the user.